1. Field of the Invention
The present invention relates to a digital copier or multiple-function image processing device. The invention is more particularly related to the system architecture of the digital copier or multiple-function image processing device.
2. Discussion of the Background
Digital copiers are image processing devices which scan an image, store a digital representation of the image in memory, and print the digital representation of the image. In order to print the digitized images at a rate similar to rates produced by conventional analog copiers which never store a digital representation of the image but use optical components such as mirrors and lenses to generate an image on a photoconductive drum or belt, a very large amount of data must be moved at a high rate of speed through the digital copier. The requirement to quickly move such a large amount of data has pushed the capabilities of current data processing and storage devices to their limits.
In the past, in order to make a digital copier, engineers have only been concerned with the immediately assigned task and were not overly concerned with the future expandability or modifications of the system architecture. The most important goal of prior digital copier systems was to build the most affordable system at the time of design with the necessary capabilities of processing large amounts of data. The result of this design and thought process was a digital copier which was produced at the lowest possible price but could not be easily modified or expanded. For example, conventional digital copiers use a proprietary bus system for communicating data and often have controllers which have the capabilities of handling only the basic copying functions. However, modifications to the system were relatively expensive and limited. The most basic function required to be performed by a digital copier is to copy a scanned image onto a new sheet of paper. However, other functions which may be desired in a digital copier include interfacing the digital copier to a personal computer or network of computers so that a scanned image obtained from the scanner of the digital copier can be provided to the personal computer or network. Similarly, it is desirable to use the digital copier as a printer to print an image from a computer or a computer network. Still further, it may be desirable to use the digital copier as a fax machine. Providing a digital copier with the ability to perform other functions makes the digital copier a multi-function machine. Thus, a multi-function machine may be considered a digital copier and vice-versa.
Because of the desire to make the base price of a digital copier as low as possible, conventional digital copiers required additional controllers such as microprocessors to perform the additional functions. For example, if it is desired to add a facsimile transmission and receiving function to a conventional digital copier, there is typically required the need to add a new facsimile controller to the system. The facsimile controller includes the basic hardware and software functionality and its own processor. The processor used by the digital copying function is typically not relied upon to perform processing duties related to facsimile transmission and receipt. Conventionally, it simply has not been possible to increase the capabilities or modify the capabilities of a digital copier by adding an inexpensive piece of computer hardware to the digital copier and upgrading the control program used by the digital copier. What has been necessary is the addition of a new control unit or controller card having both the hardware and software capabilities for performing the additional functions. The use of this additional controller card results in a duplicity of system components such as an additional, relatively expensive, microprocessor, and also a corresponding program storage memory.
Further, since the addition of components required the addition of tightly integrated hardware and software, the abilities of the added components were not flexible. For example, in a digital copier, facsimile images are transmitted and received at a speed which is far less than the capabilities of the data transmission rates of the digital copier. Thus, the system architecture of a conventional digital copier would permit the addition of two facsimile devices so that two facsimiles could be transmitted and/or received using two different phone lines. However, the demand for such a system would probably be quite low, but a very expensive tightly integrated hardware and software solution would need to be developed, making the commercial viability of such a system having the capability to send and/or receive faxes using two different phone lines quite low and impractical.